This book is a passionate plea to convince the reader Macedonia (or FYROM, if you prefer) is infract of Serbian ethnicity and not Bulgarian.
Given the publishing date (1918) it is clearly an effort to sway opinions following the second Balkan War.
The author, T.R. Georgevitch does not make any effort to hide his disdain for Greeks, Turks or Bulgars. Whatever truths might be contained in this text, they are sullied by an author who clings to personal biases.
He ends his book with a list of names, all said to be murdered at the hands of Bulgar propagandists who were trying to eradicate Serbian schools (a believable concept). His tally is 466. However, he offers no evidence to back up these lists. He does reprint some letters to treaty makers at the end of the Second Balkan war from Macedonians pleading to be joined with Serbia, however.
This book is not very useful for historical study of Macedonia. It does show the biases of the people of the area at the end of the Second Balkan War, however, and in that context, it is useful.